The Effect of Hydrogen Ion Bombardment on Fluorocarbon Polymers
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THE EFFECT OF HYDROGEN ION BOMBARDMENT ON FLUOROCARBON POLYMERS TERESA L.
CHEEKS AND ARTHUR L.
RUOFF
Dept. of Materials Science and Engineering, Cornell University Ithaca, N.Y. 14853 ABSTRACT Polytetrafluoroethylene(PTFE), Polyvinylidene fluoride(PVFD), and Polymethylmethacrylate(PMMA) thin films have been bombarded with a H2 ion beam. The ion exposure time varied from 3 to 12 minutes corresponding to an ion dose
of 101 7H+/cm2 to 1018 H+/cm2 . ESCA spectra showed that the
fluorine intensity from the fluorocarbon polymers decreased after H2 ion bombardment. Also the CF 2 type bond groups observed in the fluorocarbon polymers decreased leaving only the hydrocarbon type bond groups (CH 2 ) after H12 ion bombardment. We speculate that the hydrogen atoms abstract fluorine from the polymer which decreases the fluorine concentration. ESCA has been used to determine the effect of chemical vs. inert (H2 vs. He) ion bombardment on fluorocarbon polymers as a function of exposure time. The implication of these results to explain the differences between RIE and RIBE deposited polymers will be discussed.
INTRODUCTION The role of low energy hydrogen ion bombardment on polymeric materials used in semiconductor devices has become increasingly important. Hydrogen plasmas have been found to effectively remove organic films.[1,2] Anisotropic etching has been achieved for H12 plasma etching of conventional photoresists and polyimide.[3] An ion assisted mechanism with CH4 as the volatile product was suggested. Hydrogen RIE has also been found to reduce the 0 etch resistance in organometallics.[4] Preferential remova? of metal atoms by hydrogen to form volatile hydrides was proposed for the reduction in etch resistance. In our laboratory hydrocarbon-like polymer deposits have been observed as a result of CF 4 +H2 Reactive Ion Beam Etching(RIBE) of Si. However, based on the polymer precursers(-CF 2 -) and results from as-deposited CF 4 +H2 Reactive Ion Etching(RIE) the polymer should be a fluorocarbon. This investigation was performed to determine whether H12 ion bombardment has an effect on the surface chemistry of fluorocarbon polymers. The as-deposited RIE and RIBE polymers were simulated using thin films of hydrocarbon PMMA and fluorocarbon PVFD (CF 2 -CH 2 ) and PTFE(CF 2 -CF 2 ). This paper will discuss the effect of low energy(
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